Medical devices for subcutaneous use are known in the medical field. For example, biopsy needles are used to capture and remove internal tissues while avoiding invasive surgery. When performing medical procedures, often targeted bodily areas are surrounded by blood vessels or internal organs which can cause difficulties with accurate percutaneous positioning of medical devices. Imaging methods can mitigate some of these difficulties by providing for simultaneous imaging of internal organs and medical devices. Ultrasound imaging is particularly suitable due to its lesser operation cost and increased portability in comparison to other imaging modalities such as X-ray and MRI. During ultrasound imaging procedures, a transducer emits ultrasound waves. A portion of the ultrasound waves reflect when encountering organs, tissues, and other items inside the body and then return to the transducer. The returned sound waves are then used to produce a visual representation of an internal cavity. This provides a real-time moving image of the internal organs and medical device which a physician can use to guide the medical device to the desired bodily area.
Problems exist with current uses of ultrasound imaging to place a medical device subcutaneously because the image obtained through ultrasound is not always clear. Several factors can affect ultrasonic visibility of a medical device. For example, the density of the material that the device is constructed of, the surface structure of the device, and the angle of the device relative to the transducer each affect ultrasonic visibility of the device. When the image clarity suffers, the observation and positioning of the medical device can be more imprecise. This can enhance the risk of inadvertent damage to surrounding tissues or incorrect tissue excision in the case of biopsy.
To increase image clarity, echogenic enhancements which cause an altered or improved reflective response of ultrasound waves can be applied to a medical device and can cause greater ultrasound image clarity of the device. This in turn can increase accuracy when positioning the medical device. For example, it is known to apply echogenic enhancements near the tip of a needle so that the tip location is known with greater accuracy. However, if the needle angle changes relative to the transducer angle, the quality of the signal reflected back to the transducer degrades. As another example, it is known to apply echogenic enhancements that extend above a needle surface to increase echogenicity; however, during use in a patient these enhancements can apply drag force and thereby cause tenting of a blood vessel into body tissue upon needle removal. Drag force or tenting of the blood vessel or other body tissue is painful for the medical patient and causes trauma to vessels and body tissue. Additionally, while ultrasound technology has advanced to allow use of a wider range of ultrasound frequencies, standard echogenic enhancements allow the device to be clearly shown under a limited range of transducer frequencies. Thus, there is a need for echogenically-enhanced medical devices which can provide an ultrasound image that is more consistent and having better quality across a range of insertion angles and frequencies and body areas. Such echogenically-enhanced medical devices can improve the physician's confidence in placing a medical device.
Thus, there is a need for improvement in this field.